Due to the amount of electronic equipment which must be packaged into airborne devices such as missiles and projectiles, it is necessary to reduce the volume and weight of such circuit components as much as possible. The circuit card area which can be packed with circular, flat cards is 1.2 times the area which can be packed with rectilinear, flat cards. The circuit card area which can be packed with a spirally rolled flexible circuit card is 1.8 times the area which can be packed with a rectilinear, flat card.
Rectilinear cards which are stacked in parallel arrangement normally need a mother board at the end for interconnection. Circular printed circuit cards stacked in parallel arrangement often encounter interconnect and cross talk problems.
Thus, the spirally wound configuration is very desirable. However, the spirally rolled card must have good electrical connection; be able to dissipate heat from the electronic components; and be able to withstand substantial shock.
A spirally rolled card has been proposed in U.S. Pat. No. 2,702,853. This construction utilizes external fasteners connected to the circuit card which create additional weight. Also, this construction cannot be processed through the usual wave solder both used in electronic assembly so the cost is high. U.S. Pat. No. 2,647,224 discloses a folded circuit strip which provides complicated fold over loop sections for retaining components in position and utilizes hard wire connections which add to the weight of the device.